1. Field of the Invention
The present invention relates to surgery and, more particularly, to a system and method for positioning, moving and locating surgical instruments for performing surgery on a patient.
2. Prior Art
Recent advances in medical imagining technology (CT, MRI, PET, etc.), coupled with advances in computer-based image processing and modelling capabilities have given physicians an unprecedented ability to visualize anatomical structures in live patients, and to use this information in diagnosis and treatment planning. The precision of image-based pre-surgical planning often greatly exceeds the precision of actual surgical execution. Precise surgical execution has been limited to procedures, such as brain biopsies, in which a suitable sterotactic frame is available. The inconvenience and restricted applicability of such a frame or device has led many researchers to explore the use of robotic devices to augment a surgeon's ability to perform geometrically precise tasks planned from computed tomography (CT) or other image data. The ultimate goal of this research is partnership between a man (the surgeon) and machines (computers and robots), that seeks to exploit the capabilities of both, to do a task better than either can do alone. Machines are very precise and untiring and can be equipped with any number of sensory feedback devices. Numerically controlled robots can move a surgical instrument through an exactly defined trajectory with precisely controlled forces. On the other hand, the surgeon is very dexterous. He is also quite strong, fast, and is highly trained to exploit a variety of tactile, visual, and other cues. "Judgementally" controlled, the surgeon understands what is going on in the surgery and uses his dexterity, senses, and experience to execute the procedure. However, the surgeon usually wants to be in control of everything that goes on. If the surgeon desires to increase precision within acceptable limits of time or with sufficient speed, he must be willing to rely on machines to provide the precision.
One potential problem with a robotic device is undesired motion. The most obvious way to prevent a robotic device from making an undesired motion is to make it incapable of moving of its own accord. Motor-less manipulators have been implemented in the past which use joint encoders to provide feedback to the surgeon on where his instruments are relative to his image-based surgical plan. European Patent Application 326,768A2 describes one such device. One important limitation of this approach is that it is often very difficult for a person to align a tool accurately in six degrees-of- freedom with only the use of positional feedback. Passive manipulators, permitting free motion until locked, have also been implemented in the past for limb positioning, tissue retraction, instrument holding, and other applications in which accuracy is not important. A three degree-of-freedom passive manipulation aid for prostate surgery has also been used clinically in the past.
In cases where only a single motion axis is required during the "in contact" phase of the surgery, a robot has been used in the past essentially as a motorized sterotactic frame. A passive tool guide is placed at the desired position and orientation relative to the patient. Brakes are applied and robot power is turned off before any instrument touches the patient. The surgeon provides whatever motive force is needed for the surgical instruments themselves and relies on his own tactile senses for further feedback in performing the operation. This approach ameliorates, but does not entirely eliminate, the safety issue raised by the presence of an actively powered robot in close proximity to to the patient and operating room personnel. Furthermore, maintaining accurate positioning is not always easy, since many robots tend to "sag" a bit when they are turned off or to "jump" when brakes are applied. Leaving power turned on and relying on the robot's servocontroller to maintain position introduces further safety exposures. Finally, this type of approach is limited to cases where a fixed passive guide suffices. The surgeon cannot execute a complex pre-computed trajectory by use of this approach, nor can he precisely relocate an instrument or body part from one place to another.
Over the past several years, researchers at IBM and the University of California at Davis developed an image-directed robotic system to augment the performance of human surgeons in precise bone machining procedures in orthopedic surgery, with cementless total hip replacement surgery as an initial application. This application inherently requires computer controlled motion of the robot's end-effector while it is in contact with the patient. Thus, considerable attention had to be paid to safety checking mechanisms. In-vitro experiments conducted with this system demonstrated an order of-magnitude improvement in implant fit and placement accuracy, compared to standard manual preparation techniques. A clinical trial on dogs needing hip replacement operations is presently underway.
It is the objective of the present invention to provide a new and improved system and method for augmentation of surgery.